There are many wild bird feeders on the market, which provide considerable enjoyment to individuals, who can spend time observing the birds as they come to feed. Some feeders have been specifically designed to prevent squirrels from gaining access to the feed. Some feeders have been specifically designed to provide some sort of exhibition of the natural behavior of the wild birds as they feed.
There have also been some domestic animal self-feeding systems. These were specifically designed to provide a domesticated animal (house pet or livestock) with access to feed when there are no human attendants to dispense the feed. This required that the animal had to have some sort of training to operate the machine.